In numerous industrial applications, such as in food or chemical processing plants, and, in particular wood pulp handling and processing plants and paper manufacturing plants, the need arises to employ pipes formed from a material which is highly resistant to corrosion or etching by the conveyed fluids, and which is non-reactive with the fluid to be conveyed and non-contaminating to that fluid. Stainless steel commonly is employed for this purpose. However, stainless steel is a high cost material requiring economies to be effected in its usage. As a consequence, the wall thickness of the pipes must be kept as small as is possible within the design and operating parameters of the plant, it being uneconomical to employ stainless steel pipes of a maximum wall thickness, except in those circumstances which require maximum wall thickness. Commonly, such pipes formed from stainless steel are of a relatively light gauge and have a wall thickness in the range of 0.078 to 0.109 inches, the range not necessarily being limited to such thickness.
While such selection of minimal wall thickness of the pipes is admirable for the reasons of economy, it tends to preclude the use of quick-connect couplings, in that a quick-connect coupling of specific dimensions must be provided for any specific wall thickness of pipe.
This requirement arises in that the end faces of the coupling members must be brought into face contact with the faces of the opposite coupling member, for otherwise, there will be a gap existing between the mutually presented pairs of end faces which will permit the extrusion or cold flow of the gasket member at the interface of the coupling members, with a consequential loss of sealing pressure exerted on the elastomeric seal and seepage axially of the pipe ends, and, seepage at the radial interface of the gasket members in those instances where the elastomeric seal is other than continuous.
This condition will arise when the outside diameter of a pipe is greater than that for which the coupling was designed. In the event that the outside diameter of the pipe is less than that for which the coupling was designed, then the end faces of the coupling members will come into face contact with each other, but, prior to the required compressive force being developed within the gasket member sufficient to ensure against seepage axially of the elastomeric seal or radially at the interface of the respective ends thereof.
Further, in the event that a coupling is applied to a pipe having an outside diameter which is less than that for which the coupling was designed, and the pipe is of the type having spaced radially extending arcuate projections for interlocking with the coupling, then, the interengagement between the projections and the coupling will be of diminished extent and will reduce the strength of the interconnection.